The present invention relates generally to improvements in rooting media, improvements in methods for making such rooting media including improved release agents therefor, and an improved rooting media and method for use in propagation of plants by air layering.
Rooting media comprising soil mixture and synthetic organic resin polymers have been disclosed in prior patents, for example, U.S. Pat. No. 3,373,009 granted Mar. 12, 1968 to Malcom E. Pruitt and Joseph M. Baggett, U.S. Pat. Nos. 3,805,531 and 3,805,532 granted Apr. 23, 1970 to John F. Kistner, and U.S. Pat. No. 3,812,619 granted May 28, 1974 to Louis L. Wood and Kurt C. Frishch.
Referring first to the Kistner patents Nos. 3,805,531 and 3,805,532, these patents disclose rooting media that are formed by first mixing a prepolymer with aggregate or soil mixture and then adding water into that mixture. This method serves to infuse the prepolymer into the interstices of the aggregate or soil mixture, thereby tending to block those interstices and also to coat the exposed surface of the individual particles. This limits water infiltration and aeration of the rooting media and surface phenomena such as ion exchange. Since the prepolymer reacts quickly with water, a skin tends to form around the particles of soil mixture this giving a granular material with large pore spaces and corresponding large passageways therethrough. As a result, low capillary water content is achieved in the rooting media, so that it is necessary to water more often and there is a substantially lower field capacity, i.e., ability of the rooting media to hold water after a twenty-four hour period of draining and evaporation; likewise the rooting media is subject to quickly drying in air. The surfaces of the particles of soil mixture are essentially covered, i.e., the prepolymer flows into the soil interstices and covers the surfaces which ordinarily provide colloidal contact exchange with roots growing thereagainst; likewise the resulting rooting media have poor water holding capacity, low ion exchange capacity and low pH buffering capacity.
Referring to the Wood et al. U.S. Pat. No. 3,812,619, this patent shows the method of forming rooting media wherein the aggregate or soil mixture are mixed with water to form a first mixture. The first mixture is thereafter poured into a body of the prepolymer. Using this method, it is necessary to have a higher prepolymer concentration in order to obtain a cohesive mass. As a result, the rooting media produced thereby is rubbery in nature, so that seeds planted beneath the surface thereof have severe difficulty in sprouting therethrough, roots have difficulty in growing therein, and it is difficult to obtain adequate watering thereof. The method used by these patentees also provides for greater foaming so that the resultant rooting media are less dense with large cells and correspondingly large passageways therethrough. As a result lower capillary water content is obtained so that it is necessary to water more often, and a lower field capacity is achieved, i.e., the ability of the rooting media to hold water after a twenty-four hour period of draining and evaporation; likewise, the rooting media are highly susceptible to rapid air drying. In addition there is a formation of a rather impenetrable skin at the exposed areas, thus discouraging sprouting of seeds therethrough and the passage of water thereinto. There also is a relatively lower soil-like material content in the resultant rooting media, giving a lower ion exchange capacity, a lower water holding capacity and a lower pH buffering capacity. As a result, it is necessary to fertilize more frequently and there is a greater loss of fertilizers through leaching.